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Abstract

Optical feedback tolerance is experimentally investigated on a 600-μm-long quantum-dash based Fabry-Pérot laser emitting at 1.57μm. While quantum-dashes are structurally intermediate to quantum-wells and quantum-dots, the observed behaviour is distinctly like that of a quantum-well based laser but with greater stability. Coherence collapse and low-frequency fluctuation regimes are observed and are reported here. The onset of the coherence collapse regime is experimentally determined and is found to vary from -29 dB to -21 dB external feedback level when increasing the current from twice to nine times the threshold current.

Figures (8)

Experimental setup 1. The device under test was coupled using a lensed fibre to a 90/10 single-mode power splitter. The power meter was used to estimate the feedback level and the OSA was used to determine the onset of coherence collapse.

Experimental setup 2. The output from one facet of the device was focused by a high NA aspheric lens onto a broadband mirror. The output from the other facet was collimated through a free-space isolator and coupled to a single mode fibre isolator connected either to an OSA, an electrical spectrum analyser (ESA) or to a 6 GHz real-time oscilloscope. The OSA, ESA and oscilloscope were used to determine the onset of the CC and LFF regimes.